Download 1. What is the difference between dc and ac? Direct

1. What is the difference between d.c. and a.c?
Direct current passes in the same direction
Alternating current constantly changes direction.
2. How does a circuit breaker work?
When a current is too great the live wire breaks
in the circuit breaker.
3. What is the advantage of a circuit breaker over a
fuse?
You can reset a circuit breaker rather than
having to replace a whole fuse.
4. How does a fuse work?
If the current in a fuse is too high the fuse melts
breaking the circuit.
5. What does P = I x V work out?
Power = current x voltage
6. What does P = E / t work out?
Power = energy / time
7. Draw and label the structure of an atom
8. How are ions formed?
An atom loses or gains electrons
9. How can we identify an alpha particle?
2 neutrons + 2 protons. The same as a helium
nucleus.
10. How can we identify a beta particle?
Electron from the nucleus
11. What is the half life of a substance?
Average time for the number of nuclei of the
isotope in a sample to halve.
12. What is nuclear fission?
Splitting of an atomic nucleus
13. What is nuclear fusion?
Joining of two atomic nuclei together
14. How do alpha, beta and gamma radiation differ
in penetration power?
Alpha and beta can be deflected by both electric
and magnetic fields.
Gamma cannot.
15. What is an isotope?
An atom with a different number of neutrons,
but same number of protons and electrons.
16. How can we identify a gamma particle?
EM radiation
17. What must happen for nuclear fission to occur in
a radioactive ample?
Must absorb a neutron.
18. What happens to material that gains electrons?
It becomes negatively charged.
19. What happens for an insulator to become
negatively charged?
An excess of electrons
20. What material gains a charge?
An insulator
21. What happens for an insulator to become
positively charged?
A lack of electrons relative to protons
22. What happens when you bring together two
objects with like charges?
They repel
23. What happens when you bring together two
objects with opposite charges?
They attract
24. How would you calculate resistance?
Potential difference = current x resistance
25. What is the purpose of defibrillation?
Delivers a controlled electric shock to a heart to
restart it.
26. What does the electric shock do to the heart in
defibrillation?
Restart it
27. How does the operator of a defibrillator ensure
there is a good electrical contact with the
patients chest?
Uses a gel
Removes clothing
28. Give two advantages of having charged paint
droplets in an electrostatic paint sprayer?
Less waste and therefore less cost
More even finish
29. Why does the paint spread out on leaving the
electrostatic paint sprayer?
The positively charged paint droplets repel each
other.
30. Why are bicycle frames / cars given the opposite
charge to the paint?
So that the positively charged paint droplets
stick to the frame/car
31. Why is an electrostatic precipitator placed in
power station and factory chimneys?
Reduce pollution and removes harmful particles
32. What type(s) of power station need an
electrostatic precipitator?
Fossil fuels
33. What should you look for if a lamp does not
light?
Is there a gap in the circuit
34. What effect does a variable resistance have on
the brightness of a lamp?
It can either increase resistance or decrease
resistance.
Decreasing resistance, increases current and
increases the brightness of the lamp
In parallel
35. How should a voltmeter be placed into a circuit?
36. What type of wire brings the electrical supply
into the house?
Live (brown)
37. What type of wire provides the return path for
the electrical supply in the house?
Neutral (blue)
38. What are the colours and roles of the 3 different
wires in a plug?
Live (brown) – carries high voltage into the
house
Neutral (blue) – completes the circuit
Earth (yellow/green) – connect to case to
prevent it becoming live
39. If there are only 2 wires in a plug which ones are
included? Why could only 2 wires be in the plug?
Brown and blue.
Why? Because the Earth wire is not needed
with a ‘double insulated’ appliance
40. Which wire is the safety wire?
A fuse
41. Why is a fuse a good safety device?
The fuse is a thin wire which melts if the current
is too high. This stops the current flowing and
avoids damage or electrocution.
42. How do you know which fuse to choose?
Choose a fuse with a slightly high amps (A) than
the normal current of the appliance.
43. What is ultrasound?
A high frequency pressure wave containing
compressions and rarefractions.
44. What is meant by a longitudinal wave?
The wave direction is parallel to the vibrations
45. What is meant by the frequency of a wave?
The number of waves over a set period of time.
46. Explain how sound travels through the air to
reach your ear
Air particles vibrate. Compressions of air
particles in between periods of rarefraction send
the sound to the ear.
47. How does the frequency of a note change if its
pitch increases? (goes higher)
The frequency increases
48. What happens if you change the amplitude of a
wave?
The sound becomes louder
49. Give two other uses of ultrasound than for baby
scans
Investigate tumours
Measure the speed of blood flow
50. What is the advantage of a pregnant woman
having an ultrasound scan?
Ultrasound does not harm living cells like an x
ray.
Ultrasound have good resolution – you can
measure tissues.
Diagnosis is identifying a problem
Therapy is the treatment
51. In medicine, what is the difference between
diagnosis and therapy?
52. Give one similarity and one difference between
x-rays and gamma rays.
Both ionising electromagnetic waves
Have similar wavelengths
53. Why are X-rays and gamma rays suitable to treat
cancer patients?
They kill cells
54. Why are alpha and beta particles not suitable to
treat cancer patients?
Alpha radiation is absorbed by the skin
Beta radiation doesn’t pass through bone.
55. Give another use (than radiotherapy) of gamma
radiation in hospitals
Sterilising medical instruments and equipment
(make very clean)
56. What is a radioactive tracer?
A substance used to investigate a patient’s body
without surgery
57. Why is a radioactive tracer used?
You can detect the tracers movement with a
gamma camera.
Allows you to identify where there is a problem
without the need for surgery.
The tracer would be in the body whilst it is
tracked.
The tracer won’t last in the body and potentially
cause problems.
Gamma rays
58. Why would a short half life be useful for a
radioactive tracer?
59. Which type of nuclear radiation is stopped by
several sheets of paper?
60. What is meant by background radiation?
Radiation always present in the environment
61. Suggest two natural sources of background
radiation
Cosmic rays from space
Man-made sources from hospitals and industry
Present in rock
62. Why is alpha radiation more suitable than either
gamma or beta radiation for use in a smoke
alarm?
Alpha particles are blocked by smoke meaning
the current can’t pass through and the alarm
sounds
63. Explain how the smoke alarm works
Without smoke, alpha particles leave ions in the
air which allow a current to pass around inside.
With smoke the alpha particles are blocked and
the current can’t travel. An alarm sounds.
The source of energy provides heat to boil the
water to produce steam. The pressure of the
steam turns the turbine which turns the
generator making electricity.
64. Explain how a power station makes electricity
65. What element is used as the fuel in a nuclear
power station?
Uranium fuel rods
66. What is meant by fission?
Splitting of a nuclei
67. What is the difference between a nuclear reactor
in a power station and a nuclear bomb?
Nuclear reactor is a controlled fission (splitting)
A bomb is uncontrolled
68. How can materials be made radioactive?
Bombard the atoms with neutrons
69. Suggest one method of disposing of lower level
radioactive waste
The waste is covered in concrete and put in the
sea.
70. How can you get an electrostatic shock?
If you become charged and then become
earthed.
71. What happens if you put like charges together?
They repel
72. What happens if you put unlike charges
together?
They attract
73. What causes electrostatic events (phenomena)?
Transfer of electrons
74. How do you have a positive charge?
Due to an excess of electrons
75. How do you have a negative charge?
Due to a lack of electrons
76. Explain how static electricity can be dangerous.
(2)
Explosions can occur if static electricity occurs in
inflammable gases or with high concentrations
of oxygen.
In situations where large amounts of charge can
flow through the body to earth
77. Explain how static electricity can be annoying (2)
78. How can you reduce the chance of getting an
electric shock?
79. Explain how static electricity can be useful for
electrostatic dust precipitators to remove smoke
particles from chimneys
80. Explain how static electricity can be useful for
paint spraying
81. Explain how static electricity can be useful for
restarting the heart
Dirt and dust can become attracted to Tv
monitors
Cause clothing to cling.
Correct earthing
Use of insulating mats
Using shoes with insulating soles
Bonding fuel tanker to aircraft
Dust passes through charged metal grids
Dust particles become charged
Plates are charged opposite to grid
Dust particles are attracted to plates
Plates stuck and dust falls to collector
Spray gun charged
Paint particles charged the same so repel giving
a fine spray/coat
Object charged oppositely to paint
Attracts paint to the object giving an even coat
with less waste
Paddles charged
Electrical contact with patient’s chest
Charge passed through patient to make heart
contract
82. What happens to the resistance/current in a
circuit if you make a wire longer?
The resistance becomes greater
The current is lowered
83. What happens to the resistance/current in a
circuit if you make a wire thicker?
The resistance is reduced
The current increases
84. What is resistance measured in?
(think that there is more space for the electrons
to pass through and they do so easier)
Ohms
85. A ‘double insulated’ appliance means what?
It does not need to be earthed. The appliance is
a non-conductor and cannot become live.
86. How to calculate the distance using echos?
Use the echo time and speed of sound.
Remember to divide by two as the sound goes to
the object and back.
87. Recognise that ultrasound can be used in
medicine for diagnostic purposes (find out what
is there)
Look inside people by scanning the body
Measure the speed of blood flow in the body
88. Describe the features of longitudinal waves
89. Why can we not hear ultrasound?
90. Give uses of ultrasound
91. How can we measure radioactivity?
Wavelength (how long between waves)
Frequency (the number)
Compression (region of higher pressure)
Rarefraction (region of lower pressure)
The frequency is higher than the upper
threshold of human hearing (20,000 Hz)
Detecting babies
Diagnose problems inside the body
Produce images of soft tissues
Break down kidney stones
Measure the number of nuclear decays emitted
per second
92. What makes an ion?
Either losing an electron or gaining an electron
93. What happens to a nucleus when an alpha
particle is emitted?
Mass number decreases by 4
The atomic number decreases by 2
94. Describe what happens to a nucleus when a beta
particle is emitted
95. How are tracers used?
96. Where does background radiation comes from?
Nucleus has 2 fewer neutrons and 2 fewer
protons.
Mass number is unchanged
The nucleus has one less neutron, nucleus has
one more proton.
New element is formed.
To track waste dispersal
To find leaks/blockages in underground pipes
To track the passage of food/liquid in the body –
look for blockages
Rocks and cosmic rays
Some from industry and hospitals
97. What sources are used in smoke detectors?
Alpha sources
98. How does a smoke detector work?
Smoke particles hit by alpha radiation
Less ionisation of air particles
Current is reduced causing alarm to sound
99. Explain how radioactive dating of rocks works
Work out the uranium/lead ratio.
100. Explain how measurements of the activity of
radioactive carbon can be used to work out the
age of a material
101. Describe some similarities between x-rays
and gamma rays
102.
How is nuclear radiation used in medicine?
When an object dies exchange of air stops
As the carbon-14 decays in the sample
The ratio from living matter is used to calculate
the age within known limits
Both are ionising electromagnetic waves
Have similar wavelengths
Produced in different ways
Treatment of cancer using gamma rays
Sterilisation of equipment
103. What radioactive particles can pass through
skin?
Beta and gamma rays
104. Describe some differences between x-rays
and gamma rays
X-rays are made by firing high speed electrons at
metal targets
X-rays are easier to control the gamma rays.
105. Describe how electricity is generated at a
nuclear power station
Nuclear reaction
Produces heat
Heating water produces steam
Spin a turbine
Driving a generator
Uranium nucleus hit by neutron
Causes nucleus to split
Energy released
More neutrons released
A nuclear bomb has radioactive chain reactions
that have gone out of control
106.
How does uranium release energy
107. What is different about a nuclear bomb and a
nuclear reactor for electricity?
108.
Explain what is meant by a chain reaction
109. How do scientists stop nuclear reactions
going out of control?
Uranium nucleus splits more than one neutron is
given out
These neutrons can cause further uranium
nuclei to split
Roads placed in the reaction
Absorb some of the neutrons
Allowing enough neutrons to remain to keep the
process operating
Fusion happens when 2 nuclei join together
Fusion produces large amount of heat energy
Fusion happens at extremely high temperatures
110.
Describe how nuclear fusion releases energy
111.
Describe why fusion for power is difficult
Needs high temperatures
High temperatures have to be safely managed
112.
How does fusion happen in stars?
Extremely high temperatures and pressures